Is the programming in the TCM different or not in the TCM for a 8.1L or Duramax of any given year (Say 2003 8.1/6.6 or 2006 8.1/6.6)? If it's the same, does it base the shift points off information from the ECM?
So you could take a TCM from a truck with the 8.1, install it ina truck with the Duramax, and it should shift right?Typically the programs change every year. Sometimes, like in MY01 and MY02, there are also service releases.
The Allison bases the shift pattern on engine torque or throttle (from the engine module) and output speed at the trans.
Remeber the Duramax ECM changed for the LLY... I THINK the 2001-2004 had two long connectors like the 8.1 ECM, but the LLY ECM has three connectors (But you know that already ).yeah, ive been wondering too....because the 2006 8.1 ECMs as far as I know, are the old 16-bit ECM's that the 2001-2005 Duramax runs. That proves that the old generation ECM's have the capability to communicate on a J1939 CAN/databus level with the older ECM's...
how is Class II even close to being fast enough for ECM-to-TCM communication on the 8.1?? I thought its data rate was only like 12k/sec or soemthing slow like that (not as slow as E&C tho!). And I thought that was one of the reasons for implementing J1939 on the Dmax....it needed soemthing FAST to talk to the TCM with. THis wasnt an issue on teh gassers because the trans is controlled by the ECM (or rather 'PCM'). The 8.1 ECM would still need a much fatser means of communication than Class II I would think...The 8.1L only uses Class II.
Ok... Makes sense. Back to the drawing board (Crawls back into hole)...No, you could never exchange a Duramax program with a 8.1L. The Duramax uses J1939 (which changed to GMLAN for MY06) and Class II for communication. The 8.1L only uses Class II.
Both the Allison and the Duramax have new controllers for MY06.
Now, you can exchange a 8.1L 3.73 axle program with a 8.1L 4.10 (and vice versa) but your shift points will be off.
Perfect thanks...thats what I needed to know.The TCM for the MY06 Duramax and 8.1L is physically the same, but the programs are different.
Thanks...that was also information that I needed to confirm.but the 8.1L controller is the same for MY01-MY06.
Didnt know that! Now I do...thanks. I always thought realtime data like VSS information could not be transmitted over Class II simply because its too slow. Which is why on Escalade TNR nav units, they have a dedicated VSS line going into them, whereas the 6-disc changer radios (which need VSS data to operate the speed compensated volume) just picked up VSS data thru the data bus, but this was too slow for the real time VSS data that the nav units need, thus its requirment for a dedicated VSS input.The 8.1L does run on Class II and it is slow. But, as it is much simpler of an engine than the Duramax it work just fine. However, those items in the 8.1L that do require a faster broadcast rate (such as the torque management) have their own dedicate wires to the TCM.
bahhh!!!! Not the answer I was looking for....but its the answer I was afraid of...The simple answer is yes, but it is not feasible unless you have someone who can rewrite both the TCM and ECM code to get the two to talk nicely with eachother. Eventhough J1939 and GMLAN are very similair, there is enough of a difference in the messaging to cause a no-go situation.
Getting the mechanical parts to turn a pre-MY06 into a six-speed is fairly easy. It's always been the software side of the conversion that makes it virtually impossible.